-<!doctype linuxdoc system>
+<!doctype linuxdoc system> <!-- -*- text-mode -*- -->
<article>
<title>ld65 Users Guide
-m name Create a map file
-o name Name the default output file
-t sys Set the target system
+ -u sym Force an import of symbol `sym'
-v Verbose mode
-vm Verbose map file
--config name Use linker config file
--dbgfile name Generate debug information
--define sym=val Define a symbol
- --dump-config name Dump a builtin configuration
--end-group End a library group
+ --force-import sym Force an import of symbol `sym'
--help Help (this text)
--lib file Link this library
--lib-path path Specify a library search path
The -o switch is used to give the name of the default output file.
Depending on your output configuration, this name may NOT be used as
- name for the output file. However, for the builtin configurations, this
+ name for the output file. However, for the default configurations, this
name is used for the output file name.
<tag><tt>-t sys, --target sys</tt></tag>
The argument for the -t switch is the name of the target system. Since this
- switch will activate a builtin configuration, it may not be used together
+ switch will activate a default configuration, it may not be used together
with the <tt><ref id="option-C" name="-C"></tt> option. The following target
systems are currently supported:
<itemize>
<item>none
+ <item>module
<item>apple2
+ <item>apple2enh
<item>atari
+ <item>atarixl
<item>atmos
<item>c16 (works also for the c116 with memory up to 32K)
<item>c64
<item>c128
- <item>plus4
<item>cbm510 (CBM-II series with 40 column video)
<item>cbm610 (all CBM series-II computers with 80 column video)
- <item>pet (all CBM PET systems except the 2001)
- <item>geos
+ <item>geos-apple
+ <item>geos-cbm
<item>lunix
- <item>atmos
+ <item>lynx
<item>nes
+ <item>pet (all CBM PET systems except the 2001)
+ <item>plus4
+ <item>sim6502
+ <item>sim65c02
+ <item>supervision
+ <item>vic20
</itemize>
There are a few more targets defined but neither of them is actually
supported.
+ <tag><tt>-u sym[:addrsize], --force-import sym[:addrsize]</tt></tag>
+
+ Force an import of a symbol. While object files are always linked to the
+ output file, regardless if there are any references, object modules from
+ libraries get only linked in if an import can be satisfied by this module.
+ The <tt/--fore-import/ option may be used to add a reference to a symbol and
+ as a result force linkage of the module that exports the identifier.
+
+ The name of the symbol may optionally be followed by a colon and an address
+ size specifier. If no address size is specified, the default address size
+ for the target machine is used.
+
+ Please note that the symbol name needs to have the internal representation,
+ meaning you have to prepend an underline for C identifiers.
+
+
<label id="option-v">
<tag><tt>-v, --verbose</tt></tag>
<tag><tt>-S addr, --start-addr addr</tt></tag>
Using -S you may define the default starting address. If and how this
- address is used depends on the config file in use. For the builtin
- configurations, only the "none" system honors an explicit start address,
- all other builtin config provide their own.
+ address is used depends on the config file in use. For the default
+ configurations, only the "none", "apple2" and "apple2enh" systems honor an
+ explicit start address, all other default configs provide their own.
<tag><tt>-V, --version</tt></tag>
written to this file. Using the <tt/-g/ option for the compiler and assembler
will increase the amount of information available. Please note that debug
information generation is currently being developed, so the format of the
- file and it's contents are subject to change without further notice.
+ file and its contents are subject to change without further notice.
<tag><tt>--lib file</tt></tag>
<sect>Search paths<p>
-Starting with version 2.10 there are now several search paths for files needed
-by the linker: One for libraries, one for object files and one for config
+Starting with version 2.10, there are now several search-path lists for files needed
+by the linker: one for libraries, one for object files, and one for config
files.
<sect1>Library search path<p>
-The library search path contains in this order:
+The library search-path list contains in this order:
<enum>
<item>The current directory.
-<item>A compiled in library path which is often <tt>/usr/lib/cc65/lib</tt> on
- Linux systems.
-<item>The value of the environment variable <tt/LD65_LIB/ if it is defined.
-<item>The value of the environment variable <tt/CC65_LIB/ if it is defined.
- Please note that use of this environment variable is obsolete and may
- get removed in future versions.
<item>Any directory added with the <tt><ref id="option--lib-path"
name="--lib-path"></tt> option on the command line.
+<item>The value of the environment variable <tt/LD65_LIB/ if it is defined.
+<item>A subdirectory named <tt/lib/ of the directory defined in the environment
+ variable <tt/CC65_HOME/, if it is defined.
+<item>An optionally compiled-in library path.
</enum>
<sect1>Object file search path<p>
-The object file search path contains in this order:
+The object file search-path list contains in this order:
<enum>
<item>The current directory.
-<item>A compiled in directory which is often <tt>/usr/lib/cc65/lib</tt> on
- Linux systems.
-<item>The value of the environment variable <tt/LD65_OBJ/ if it is defined.
-<item>The value of the environment variable <tt/CC65_LIB/ if it is defined.
- Please note that use of this environment variable is obsolete and may
- get removed in future versions.
<item>Any directory added with the <tt><ref id="option--obj-path"
name="--obj-path"></tt> option on the command line.
+<item>The value of the environment variable <tt/LD65_OBJ/ if it is defined.
+<item>A subdirectory named <tt/obj/ of the directory defined in the environment
+ variable <tt/CC65_HOME/, if it is defined.
+<item>An optionally compiled-in directory.
</enum>
<sect1>Config file search path<p>
-The config file search path contains in this order:
+The config file search-path list contains in this order:
<enum>
<item>The current directory.
-<item>A compiled in directory which is often <tt>/usr/lib/cc65/lib</tt> on
- Linux systems.
-<item>The value of the environment variable <tt/LD65_CFG/ if it is defined.
<item>Any directory added with the <tt><ref id="option--cfg-path"
name="--cfg-path"></tt> option on the command line.
+<item>The value of the environment variable <tt/LD65_CFG/ if it is defined.
+<item>A subdirectory named <tt/cfg/ of the directory defined in the environment
+ variable <tt/CC65_HOME/, if it is defined.
+<item>An optionally compiled-in directory.
</enum>
name="Configuration files">).
After that, the linker is ready to produce an output file. Before doing that,
-it checks it's data for consistency. That is, it checks for unresolved
+it checks its data for consistency. That is, it checks for unresolved
externals (if the output format is not relocatable) and for symbol type
mismatches (for example a zero page symbol is imported by a module as absolute
symbol).
the linker will first write the <tt/CODE/ segment, then the <tt/RODATA/
segment, then the <tt/DATA/ segment - but it will not write the <tt/BSS/
segment. Why? Enter the segment type: For each segment specified, you may also
-specify a segment attribute. There are five possible segment attributes:
+specify a segment attribute. There are four possible segment attributes:
<tscreen><verb>
ro means readonly
- wprot same as ro but will be marked as write protected in
- the VICE label file if -Lp is given
- rw means read/write
- bss means that this is an uninitialized segment
- zp a zeropage segment
+ rw means read/write
+ bss means that this is an uninitialized segment
+ zp a zeropage segment
</verb></tscreen>
So, because we specified that the segment with the name BSS is of type bss,
named "rom2.bin". The name given on the command line is ignored in both cases.
Assigning an empty file name for a memory area will discard the data written
-to it. This is useful, if the a memory area has segments assigned that are
-empty (for example because they are of type bss). In that case, the linker
-will create an empty output file. This may be suppressed by assigning an empty
-file name to that memory area.
+to it. This is useful, if the memory area has segments assigned that are empty
+(for example because they are of type bss). In that case, the linker will
+create an empty output file. This may be suppressed by assigning an empty file
+name to that memory area.
+The <tt/%O/ sequence is also allowed inside a string. So using
+
+<tscreen><verb>
+ MEMORY {
+ ROM1: start = $A000, size = $2000, file = "%O-1.bin";
+ ROM2: start = $E000, size = $2000, file = "%O-2.bin";
+ }
+</verb></tscreen>
+
+would write two files that start with the name of the output file specified on
+the command line, with "-1.bin" and "-2.bin" appended respectively. Because
+'%' is used as an escape char, the sequence "%%" has to be used if a single
+percent sign is required.
<sect1>LOAD and RUN addresses (ROMable code)<p>
unfortunately, ROM is not writable, so we have to copy it into RAM before
running the actual code.
-The linker cannot help you copying the data from ROM into RAM (this must be
-done by the startup code of your program), but it has some features that will
-help you in this process.
+The linker won't copy the data from ROM into RAM for you (this must be done by
+the startup code of your program), but it has some features that will help you
+in this process.
First, you may not only specify a "<tt/load/" attribute for a segment, but
also a "<tt/run/" attribute. The "<tt/load/" attribute is mandatory, and, if
goes into <tt/ROM2/. Read/write data will be loaded into <tt/ROM2/ but is run
in <tt/RAM2/. That means that all references to labels in the <tt/DATA/
segment are relocated to be in <tt/RAM2/, but the segment is written to
-<tt/ROM2/. All your startup code has to do is, to copy the data from it's
+<tt/ROM2/. All your startup code has to do is, to copy the data from its
location in <tt/ROM2/ to the final location in <tt/RAM2/.
So, how do you know, where the data is located? This is the second point,
All references to labels in the <tt/DATA/ segment are relocated to <tt/RAM2/
by the linker, so things will work properly.
+There's a library subroutine called <tt/copydata/ (in a module named
+<tt/copydata.s/) that might be used to do actual copying. Be sure to have a
+look at it's inner workings before using it!
+
<sect1>Other MEMORY area attributes<p>
}
</verb></tscreen>
-This will define three external symbols that may be used in your code:
+This will define some external symbols that may be used in your code:
<tscreen><verb>
__STACK_START__ This is set to the start of the memory
- area, $C000 in this example.
+ area, $C000 in this example.
__STACK_SIZE__ The size of the area, here $1000.
__STACK_LAST__ This is NOT the same as START+SIZE.
- Instead, it it defined as the first
- address that is not used by data. If we
- don't define any segments for this area,
- the value will be the same as START.
+ Instead, it it defined as the first
+ address that is not used by data. If we
+ don't define any segments for this area,
+ the value will be the same as START.
+ __STACK_FILEOFFS__ The binary offset in the output file. This
+ is not defined for relocatable output file
+ formats (o65).
</verb></tscreen>
A memory section may also have a type. Valid types are
Unused memory in a memory area may be filled. Use the "<tt/fill = yes/"
attribute to request this. The default value to fill unused space is zero. If
you don't like this, you may specify a byte value that is used to fill these
-areas with the "<tt/fillval/" attribute. This value is also used to fill unfilled
-areas generated by the assemblers <tt/.ALIGN/ and <tt/.RES/ directives.
+areas with the "<tt/fillval/" attribute. If there is no "<tt/fillval/"
+attribute for the segment, the "<tt/fillval/" attribute of the memory area (or
+its default) is used instead. This means that the value may also be used to
+fill unfilled areas generated by the assemblers <tt/.ALIGN/ and <tt/.RES/
+directives.
The symbol <tt/%S/ may be used to access the default start address (that is,
the one defined in the <ref id="FEATURES" name="FEATURES"> section, or the
value given on the command line with the <tt><ref id="option-S" name="-S"></tt>
option).
+To support systems with banked memory, a special attribute named <tt/bank/ is
+available. The attribute value is an arbitrary 32 bit integer. The assembler
+has a builtin function named <tt/.BANK/ which may be used with an argument
+that has a segment reference (for example a symbol). The result of this
+function is the value of the bank attribute for the run memory area of the
+segment.
+
<sect1>Other SEGMENT attributes<p>
</verb></tscreen>
If an alignment is requested, the linker will add enough space to the output
-file, so that the new segment starts at an address that is divideable by the
+file, so that the new segment starts at an address that is dividable by the
given number without a remainder. All addresses are adjusted accordingly. To
fill the unused space, bytes of zero are used, or, if the memory area has a
"<tt/fillval/" attribute, that value. Alignment is always needed, if you have
-the used the <tt/.ALIGN/ command in the assembler. The alignment of a segment
+used the <tt/.ALIGN/ command in the assembler. The alignment of a segment
must be equal or greater than the alignment used in the <tt/.ALIGN/ command.
The linker will check that, and issue a warning, if the alignment of a segment
-is lower than the alignment requested in a <tt/.ALIGN/ command of one of the
+is lower than the alignment requested in an <tt/.ALIGN/ command of one of the
modules making up this segment.
For a given segment you may also specify a fixed offset into a memory area or
of the segment in the run memory area, because this is what is usually
desired. If load and run memory areas are equal (which is the case if only the
load memory area has been specified), the attributes will also work. There is
-also a "<tt/align_load/" attribute that may be used to align the start of the
+also an "<tt/align_load/" attribute that may be used to align the start of the
segment in the load memory area, in case different load and run areas have
been specified. There are no special attributes to set start or offset for
just the load memory area.
+A "<tt/fillval/" attribute may not only be specified for a memory area, but
+also for a segment. The value must be an integer between 0 and 255. It is used
+as fill value for space reserved by the assemblers <tt/.ALIGN/ and <tt/.RES/
+commands. It is also used as fill value for space between sections (part of a
+segment that comes from one object file) caused by alignment, but not for
+space that preceeds the first section.
+
To suppress the warning, the linker issues if it encounters a segment that is
not found in any of the input files, use "<tt/optional=yes/" as additional
segment attribute. Be careful when using this attribute, because a missing
</verb></tscreen>
The only other available output format is the o65 format specified by Andre
-Fachat. It is defined like this:
+Fachat (see the <htmlurl url="http://www.6502.org/users/andre/o65/fileformat.html"
+name="6502 binary relocation format specification">). It is defined like this:
<tscreen><verb>
FILES {
The <tt/FORMAT/ section is used to describe file formats. The default (binary)
format has currently no attributes, so, while it may be listed in this
-section, the attribute list is empty. The second supported format, o65, has
-several attributes that may be defined here.
+section, the attribute list is empty. The second supported format,
+<htmlurl url="http://www.6502.org/users/andre/o65/fileformat.html" name="o65">,
+has several attributes that may be defined here.
<tscreen><verb>
FORMATS {
Please note that the order of entries with equal priority is undefined.
+ <tag><tt>import</tt></tag>
+
+ This attribute defines a valid symbol name, that is added as an import
+ to the modules defining a constructor/desctructor of the given type.
+ This can be used to force linkage of a module if this module exports the
+ requested symbol.
+
</descrip>
Without specifying the <tt/CONDES/ feature, the linker will not create any
<sect1>The SYMBOLS section<label id="SYMBOLS"><p>
The configuration file may also be used to define symbols used in the link
-stage. The mandatory attribute for a symbol is its value. A second, boolean
-attribute named <tt/weak/ is available. If a symbol is marked as weak, it may
-be overridden by defining a symbol of the same name from the command line. The
-default for symbols is that they're strong, which means that an attempt to
-define a symbol with the same name from the command line will lead to an
-error.
+stage or to force symbols imports. This is done in the SYMBOLS section. The
+symbol name is followed by a colon and symbol attributes.
+
+The following symbol attributes are supported:
+
+<descrip>
+
+ <tag><tt>addrsize</tt></tag>
+
+ The <tt/addrsize/ attribute specifies the address size of the symbol and
+ may be one of
+<itemize>
+ <item><tt/zp/, <tt/zeropage/ or <tt/direct/
+ <item><tt/abs/, <tt/absolute/ or <tt/near/
+ <item><tt/far/
+ <item><tt/long/ or <tt/dword/.
+</itemize>
+
+Without this attribute, the default address size is <tt/abs/.
+
+ <tag><tt>type</tt></tag>
+
+ This attribute is mandatory. Its value is one of <tt/export/, <tt/import/ or
+ <tt/weak/. <tt/export/ means that the symbol is defined and exported from
+ the linker config. <tt/import/ means that an import is generated for this
+ symbol, eventually forcing a module that exports this symbol to be included
+ in the output. <tt/weak/ is similar as <tt/export/. However, the symbol is
+ only defined if it is not defined elsewhere.
+
+ <tag><tt>value</tt></tag>
+
+ This must only be given for symbols of type <tt/export/ or <tt/weak/. It
+ defines the value of the symbol and may be an expression.
+
+</descrip>
The following example defines the stack size for an application, but allows
the programmer to override the value by specifying <tt/--define
<tscreen><verb>
SYMBOLS {
# Define the stack size for the application
- __STACKSIZE__: value = $800, weak = yes;
+ __STACKSIZE__: type = weak, value = $800;
}
</verb></tscreen>
-<sect1>Builtin configurations<p>
+<sect>Special segments<p>
+
+The builtin config files do contain segments that have a special meaning for
+the compiler and the libraries that come with it. If you replace the builtin
+config files, you will need the following information.
+
+<sect1>INIT<p>
+
+The INIT segment is used for initialization code that may be reused once
+execution reaches main() - provided that the program runs in RAM. You
+may for example add the INIT segment to the heap in really memory
+constrained systems.
+
+<sect1>LOWCODE<p>
-The builtin configurations are part of the linker source. They are also
-distributed together with the machine specific binary packages (usually in the
-doc directory) and don't have a special format. So if you need a special
-configuration, it's a good idea to start with the builtin configuration for
-your system. In a first step, just replace <tt/-t target/ by <tt/-C
-configfile/. The go on and modify the config file to suit your needs.
+For the LOWCODE segment, it is guaranteed that it won't be banked out, so it
+is reachable at any time by interrupt handlers or similar.
+<sect1>STARTUP<p>
+This segment contains the startup code which initializes the C software stack
+and the libraries. It is placed in its own segment because it needs to be
+loaded at the lowest possible program address on several platforms.
-If you have problems using the linker, if you find any bugs, or if you're
-doing something interesting with it, I would be glad to hear from you. Feel
-free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
-name="uz@cc65.org">).
+The ZPSAVE segment contains the original values of the zeropage locations used
+by the ZEROPAGE segment. It is placed in its own segment because it must not be
+initialized.
projects / cc65 / blobdiff